Fm Reviewer

1. The amount of frequency deviation from the carrier center frequency in an FM transmitter is proportional to what characteristic of the modulating signal? a. Amplitude b. Phase c. Angle d. Duty Cycle 2. Both FM and PM are types of what kind of modulation? a. Amplitude b. Phase c. Angle d. Duty Cycle 3. If the amplitude of the modulating signal decreases, the carrier deviation a. Increases b. Decreases c. Remains constant d. Both b and c 4. In PM, a frequency shift occurs while what characteristic of the modulating signal is changing? a. Shape b. Phase c. Frequency d. Amplitude 5. Maximum frequency deviation of a PM signal occurs at a. Zero crossing points b. Peak positive amplitude c. Peak negative amplitude d. Peak positive or negative amplitudes 6. A 100-MHz carrier is deviated 50 KHz by a 4 kHz signal. The modulation index is a. 5 b. 8 c. 12.5 d. 40 7. The maximum deviation of an FM carrier is 2 kHz by a maximum modulating signal of 400 Hz. The deviation ratio is a. 0.2 b. 5 c. 8 d. 40 8. According the Nyquist theorem, the sampling rate that can be used in a PCM system is _____ the highest audio frequency a. Once b. Eight times c. Twice d. Thrice 9. Which of the following pulse modulation systems is analog? a. Delta

b. Differential PCM c. PWM d. PCM 10. The phenomenon of a strong FM signal dominating weaker signal on a common frequency is referred to as the a. Capture effect b. Blot out c. Quieting factor d. Dominating syndrome 11. In the stabilized reactance modulator AFC system, a. The discriminator must have a fast time constant to prevent demodulation b. The higher the discriminator frequency, the better the oscillator frequency stability c. The discriminator frequency must not be too low, or the system will fail d. Phase modulation is converted into FM by the equalizer circuit 12. In the spectrum of a frequency of a frequency-modulated wave a. The carrier frequency disappears when the modulation index is large b. The amplitude of any sideband depends on the modulation index c. The total number of sidebands depends on the modulation index d. The carrier frequency cannot disappear 13. The difference between phase and frequency modulation a. Is purely theoretical because they are the same in practice b. Is too great to make the two systems compatible c. Lies in the poorer audio response of phase modulation d. Lies in the different definitions of the modulation index 14. Indicate the false statement regarding the Armstrong modulation system. a. The system is basically phase, not frequency, modulation b. AFC is not needed, as a crystal oscillator is used c. Frequency multiplication must be used d. Equalization is unnecessary 15. An FM signal with a modulation index mf is passed through a frequency tripler. The wave in the output of the tripler will have a modulation index of a. mf/3 b. mf c. 3 mf d. 9mf 16. An FM signal with a deviation δ is passed through a mixer, and has its frequency reduced fivefold. The deviation in the output of the mixer is a. 5 δ b. Indeterminate c. δ/5 d. δ 17. A pre-emphasis circuit provides extra noise immunity by a. Boosting the bass frequencies b. Amplifying the higher audio frequencies c. Pre-amplifying the whole audio band

d. Converting the phase modulation to FM 18. Since noise phase modulates the FM wave, as the noise sideband frequency approaches the carrier frequency, the noise amplitude a. Remains constant b. Decreased c. Increased d. Equalized 19. When the modulating frequency is doubled, the modulation index is halved, and the modulating voltage remains constant. The modulating system is a. Amplitude modulation b. Phase modulation c. Frequency modulation d. Any of the three 20. Indicate which one of the following is not an advantage of FM over AM a. Better noise immunity is provided b. Lower bandwidth is required c. The transmitted power is more useful d. Less modulating power is required 21. One of the following is an indirect way of generating FM. This is the a. Reactance FET modulator b. Varactor diode modulator c. Armstrong modulator d. Reactance bipolar transistor modulator 22. Indicate the false statement regarding the advantages of SSB over double-sideband, fullcarrier AM. a. More channel space is available b. Transmitter circuits must be more stable, giving better reception c. The signal is more noise resistance d. Much less power is required for the same signal strength 23. _______ determines the number of sideband components in FM. a. carrier frequency b. modulation frequency c. modulation index d. deviation ratio 24. What produces the sidebands on FM? a. signal amplitude b. carrier harmonics c. baseband frequency d. broadband frequency 25. An FM receives signal ______. a. vary in amplitude with modulation b. vary in frequency with modulation c. vary in frequency and amplitude with wideband modulation

d. is not immune to noise 26. The frequency of the unmodulated carrier in FM system is a. modulating frequency b. center frequency c. carrier frequency d. deviation frequency 27. The ratio of maximum deviation to the maximum modulating frequency is called a. carrier swing b. deviation ratio c. modulation factor d. modulation index 28. What is the modulation index of an FM signal having a carrier swing of 75 kHz when the modulating signal has frequency of 3 kHz? a. 25 b. 12.5 c. 0.04 d. 0.08 29. In a FM system, if modulation index is doubled by having the modulating frequency, what will be the effect on the maximum deviation? a. No effect b. Maximum deviation doubles c. Decreases by ½ d. Increases by ¼ 30. Which of the following is considered as an indirect method of generating FM? a. Reactance modulator b. Balanced modulator c. Varactor diode modulator d. Armstrong system 31. In FM, the Carson’s Rule states that the bandwidth is equal to twice the sum of the modulating frequency and ______. a. Carrier signal b. Modulating signal c. Frequency deviation d. Image frequency 32. What is the carrier swing of an FM transmitter when modified by 75%? a. 53.2 kHz b. 48 kHz c. 56.25 kHz d. 112.5 kHz 33. The modulation system inherently more resistant to noise a. Single sideband suppressed carrier b. Frequency modulation c. Pulse-position modulation d. Amplitude shift keying 34. Subcarriers that are arranged so that the channels occupying adjacent frequency bands with some frequency space between them is known as

a. Guard bands b. AM bands c. Band gap d. Void band e. Both B and C 35. Frequency modulation and phase modulation are collectively referred to as a. Stereo b. Angle modulation c. High fidelity modulation d. FCC modulation 36. In FM, the change in carrier frequency is proportional to what attribute of the modulating signal? a. Angle b. Frequency c. Amplitude d. Tone 37. A louder sound, when generating the modulating waveform for FM, will cause a greater a. Carrier amplitude b. Angle amplitude c. Distortion at the receiver d. Frequency deviation 38. If a positive change in modulation signal level of 200 mW will cause a positive frequency deviation of 10 kHz, what will be the frequency deviation for a negative change of 10 mV in the level of the modulating signals? a. 0 b. -5 kHz c. +5 kHz d. +0 kHz 39. A particular 15 kHz modulation tone results in a peak frequency deviation of 75 kHz. What is the modulation index? a. 5 b. 15 c. 75 d. 3 40. A 15 kHz sine wave frequency modulates an 88 MHz carrier. A sideband frequency will be found at a. 87.970 MHz b. 87.985 MHz c. 88.015 MHz d. All of these 41. A device whose capacitance is deliberately made to be a function of the applied voltage a. Varactor diode b. UJT c. SAW d. Variable capacitor 42. A reactance modulator is one method of obtaining

a. Indirect FM b. Direct FM c. Demodulation d. Low frequency filtering 43. A device, now available in IC form, is useful for direct FM and as one element in the phse-locked loop. a. AFC b. AGC c. VCO d. LPF 44. _____ is a frequency change process, whereby the phase deviation and frequency deviation are multiplied by some fixed constant. a. Translation b. Multiplication c. Division d. Addition 45. A circuit that has the function of demodulating the frequency-modulated signal. a. AFC b. Envelope detector c. Decoder d. Foster-Seeley discriminator 46. The ratio detector is superior to the slope detector because a. It is less sensitive to phase modulation b. It is less sensitive to noise spikes c. It is less sensitive to interference causing AM d. Both B and C 47. One implementation of a pulse averaging discriminator is a. A free-running multivibrator b. A crystal-controlled oscillator c. A quartz crystal filter d. A triggered multivibrator 48. A 10% increase in the frequency of a constant-width pulse train should cause what change in its average value? a. -10% b. -1% c. +1% d. +10% 49. Two different signals can be coherent if they a. Have the same amplitude b. Are both sine waves of different frequencies c. Originate in the same physical equipment simultaneously d. Have the same frequency 50. A quadrature detector requires that a. Four gates bee provided b. The inputs are coherent c. The inputs are incoherent

d. The inputs are identical 51. In a phase-locked loop, the VCO is the abbreviation for a. Variable coherent output b. VHF communication oscillator c. Voltage-controlled oscillator d. Vien-count oscillator (neutralized) 52. Identify an advantage, or advantages of a properly designed FM system. a. Relative immunity to atmospheric noise (lightning) b. Reduced bandwidth required c. No noise of any kind d. The noise figure is inversely proportional to the modulation index 53. What is the modulation index of an FM signal if its modulating frequency is doubled? a. No effect b. Twice the original index c. Four times the original index d. One-half the original index 54. _____ is the circuit used to detect frequency modulated signal. a. Discriminator b. Modulator c. Modem d. Detector 55. _____ is an information signal that is sent directly without modulating any carrier. a. C-band b. Q-band c. Baseband d. Broadband 56. Both frequency and phase modulation utilize ______ modulation. a. Digital b. Phase c. Amplitude d. Angle 57. It is the width of frequencies within the spectrum occupied by a signal and used by the signal for conveying information. a. Band b. Bandwidth c. Electronic spectrum d. Frequency band 58. ______ is kind of modulation in which the modulated wave is always present. a. Carrier modulation b. Continuous modulation c. Log-periodic modulation d. Square-wave modulation 59. A type of modulation in which no signal is present between pulses. a. Pulse modulation b. FSK c. QAM

d. PAM 60. _______ is a form of amplitude distortion introduced when the positive and negative alternations in the AM modulated signals are not equal. a. Envelope distortion b. Spurious emission c. Carrier shift d. Johnson noise 61. What is the advantage of phase modulation over direct FM frequency modulation? a. Multipliers can be used b. The deviation is smaller c. Simplicity and practicality d. The oscillator is crystal-controlled 62. If the spectrum is shifted in frequency with no other changes, this is known as a. Frequency multiplication b. Sideband movement c. Baseband reorientation d. Frequency translation 63. A device which is capable of causing frequency translation a. High-Q tank circuit b. Balanced modulator c. Low-Q tank circuit d. IF strip 64. If the frequency of each component in a signal spectrum is increased by the same fixed amount, this known as a. Modulation b. Frequency translation c. Up conversion d. Both B and C 65. A particular amplifier is designed to be a frequency doubler. If the input signal frequency is 15.4 MHz, a circuit in the output will be tuned to a. 7.7 MHz b. 15.4 MHz c. 30.8 MHz d. 61.6 MHz 66. A sine wave of 293 MHz is phase-modulated to achieve a maximum phase deviation of 0.2 radian. After passing through a frequency tripler, the maximum phase deviation will be a. 0.2 radian b. 0.3 radian c. 0.4 radian d. 0.6 radian 67. Any device to be used as a frequency multiplier must be a. Active b. Passive c. Linear d. Nonlinear

68. A particular amplifier circuit used for frequency doubling. a. Push-push b. Push-pull c. Pull-push d. Pull-pull 69. Frequency division is useful in the implementation of a a. AM demodulator b. Frequency synthesizer c. AGC circuit d. FM demodulator 70. Frequency division by 12 will require how many flip-flops in the counter? a. 3 b. 4 c. 6 d. 12 71. Identify an electronic device, not specifically designed for the purpose, which can be used as a phase detector. a. Wien bridge b. Colpitts oscillator c. Balanced modulator d. Butterworth filter 72. A particular frequency synthesizer contains only a single crystal. What words describe this synthesizer? a. Crystal modulated b. Inexact c. Indirect d. Deficient 73. A recognizable feature of a CW transmitter is a. Keyed transmitter b. Power amplification c. Frequency generation d. All of these 74. The term “pulling” refers to a. The change of the crystal oscillator frequency by loading b. One half-cycle operation of a push-pull amplifier c. Loading on the transmitter caused by the antenna connection d. Reduction of the power supply terminal voltage as the transmitter is keyed. 75. When frequency modulation is achieved by initial phase modulation, this is called a. Angular modulation b. Direct FM c. Indirect FM d. Indirect synthesis 76. A disadvantage of direct FM is the need for a. AGC b. AFC c. A frequency synthesizer

d. Phase modulation 77. Direct FM can be achieved by a. A reactance tube modulator b. A varactor diode c. And AGC circuit d. Both A and B 78. The change of the modulated carrier frequency from the original RF to the IF of the superheterodyne receiver is known as a. Frequency multiplication b. Frequency allocation c. Frequency substitution d. Frequency translation 79. The key to achieving receiver sensitivity is the reduction of a. Image response b. Mixer harmonic products c. Spurious frequency response d. Internal noise 80. An FM receiver with an I-F of 10.7 MHz is tuned to 98.7 MHz. What is the numerical value of the image frequency? a. 77.3 MHz b. 88.0 MHz c. 109.4 MHz d. 120.1 MHz 81. A source of RF interference exists at 109.9 MHz. For which frequency in the FM broadcast band will this be the image frequency? a. 21.4 MHz b. 88.5 MHz c. 99.2 MHz d. 110.7 MHz 82. The ratio of the superheterodyne receiver response at the desired carrier frequency to that at the image frequency is called a. The sensitivity b. The selectivity c. The image frequency d. The image rejection ratio 83. The core of an IF transformer usually contains a. Teflon b. Computer nylon c. Powdered iron d. Laminated steel 84. Shape factor is a measure of a. Bandwidth b. Skirt steepness c. Coupling coefficient d. Critical coupling

85. _______ is the function which tends to maintain the sound volume level of a voice receiver nearly constant for a large signal strength range. a. Squelch b. Muting c. AGC d. AFC 86. The function which tends to silence the receiver in the absence of transmitted carrier. a. Squelch b. Muting c. AGC d. AFC 87. What device is incorporated in a communications receiver to reduce impulse noise? a. Front-end processor b. Squelch circuit c. AGC d. Noise blanker 88. What type of signal in which a receiver selectivity of 2.4 kHz in the I-F circuitry is optimum? a. FM voice b. Double-sideband AM voice c. FSK data d. SBB voice 89. If the input to a detector stage is an amplitude-modulated (A3E) IF signal then the output from the stage is a. A lower frequency carrier b. The audio voice information c. A Morse-code signal d. The upper or lower set of sidebands 90. In a capacitive type, reactance-tube modulator connected across an oscillator tuned circuit, a more negative voltage on the grid of the reactance tube will cause a. An increase of the oscillator frequency b. An decrease of oscillator frequency c. An increase of the reactance-tube capacitance d. An increase of the reactance tube ac plate current 91. The limiting condition for sensitivity in a communications receiver is 92. When a communications receiver is tuned to a strong signal, the AGC bias is measured and found to be zero. The fault cannot be caused by a/an a. Defective IF stage b. Defective local oscillator c. Defective RF stage d. Open circuit in the AGC’s filter capacitor 93. The term used to refer to the condition where the signals from a very strong station are superimposed on other signals being received a. Cross-modulation interference b. Intermodulation interference c. Receiver quieting

d. Capture effect 94. The limiter stage of an FM receiver a. Behaves as a low-pass filter b. Limits the amplitude of the IF signal to the required level c. Behaves as a high-pass filter d. Behaves as a bandstop filter 95. Motorboating (low-frequency oscillations) in an amplifier can be stopped by a. Grounding the screen grid b. Connecting a capacitor between the B+ and lead ground c. By passing the screen grid resistor with a 0.1 µF capacitor d. Grounding the plate 96. An effect in which, the modulation of an unwanted signal is transferred to the desired carrier. a. Crossmodulation b. Intermodulation c. Modulation mixing d. Image-channel interference 97. Leads should be kept as short as possible in radio circuit so that a. Skin effect is reduced b. There is less hysteresis effect c. There is less dielectric loss d. Stray coupling is minimized 98. The number of voice transmissions that can be packed into a given frequency band for amplitude-compandored single-sideband systems over conventional FM-phone systems. a. 2 b. 18 c. 16 d. 4 99. Neutralization of an RF amplifier stage can be necessary in order to a. Increase the amplifier’s gain b. Prevent the generation of spurious oscillations c. Reduce the amplifier’s gain d. Reduce the level of the output harmonics 100. The ability of a communications receiver to perform well in the presence of strong signals outside the band of interest is indicated by what parameter? a. Blocking dynamic range b. Noise figure c. Signal-to-noise ratio d. Audio output 101. Stages that are common to both AM and FM receivers a. Tuner, local oscillator, detector, AF amplifier b. RF amplifier, mixer, IF amplifier, AF amplifier c. Local oscillator, RF amplifier, frequency discriminator, detector d. Tuner, IF amplifier, detector, AF amp 102. Occurs during CW reception if too narrow a filter bandwidth is used in the IF stage of a receiver

a. b. c. d.

Filter ringing Undesired signals will reach the audio stage Output-offset overshoot Cross-modulation distortion 103. What stage mainly determines a communication receiver’s sensitivity? a. IF amplifier b. Mixer stage c. Detector stage d. RF amplifier 104. What is the main advantage of FM over AM? a. Better signal-to-noise-ratio b. Narrower bandwidth c. Greater propagation range d. Total freedom from adjacent-channel interference 105. An amplitude modulation created in an amplifier before the final RF stage. a. Low-level modulation b. High-level modulation c. Direct modulation d. Indirect modulation 106. Receiver desensitizing can be reduced by a. Increasing the transmitter audio gain b. Decreasing the receiver squelch gain c. Increasing the receiver bandwidth d. Ensuring good RF shielding between the transmitter 107. In a narrow-band FM system, the deviation ratio is commonly one and the highest audio frequency is generally limited to a. 300 Hz b. 10,000 Hz c. 3,000 Hz d. 7,500 Hz 108. In a phase-modulated signal (indirect FM), the frequency deviation is directly proportional to the a. Carrier amplitude only b. Amplitude of the modulating tone and frequency of the carrier c. Carrier frequency only d. Modulating signal amplitude only 109. A system containing a limiter stage, a discriminator, and a de-emphasis circuit? a. Direct FM transmitter b. Indirect FM transmitter c. Single sideband AM receiver d. FM receiver 110. The limiter stage of an FM receiver a. Prevents any amplitude modulation of the IF signal b. Limits the amount of frequency deviation in the IF signal c. Limits the overall bandwidth of the IF stages d. Corrects any deviation in carrier frequency

111. High selectivity occurs when the degree of coupling between a receiver’s RF stages is a. Tight b. Loose c. Critical d. Adjusted for maximum power transfer 112. A carrier is phase modulated by a test tone. If the amplitude and the frequency of the tone are both doubled, the amount of the deviation is a. Doubled b. Unchanged c. Halved d. Multiplied by four 113. The degree of selectivity desirable in the IF circuitry of a single-sideband receiver. a. 1 kHz b. 2.4 kHz c. 4.2 kHz d. 4.8 kHz 114. The component most apt to break down in the radio circuit is the a. Crystal b. Resistor c. Transformer d. Diode 115. The base in an RF amplifier is grounded in order to a. Avoid the requirement of neutralizing the stage b. Raise the input impedance c. Lower the output impedance d. Obtain maximum power output 116. The AM detector performs two basic functions in the receiver. a. Rectifies and filters b. Amplifiers and filters c. Buffer and amplifier d. Buffer and detector 117. A varactor diode can be used in a/an a. Direct FM modulator circuit b. AFC circuit in a direct FM transmitter c. Phase-modulator circuit d. All of these 118. Receiver interference is not reduced by including a/an a. Crystal filter b. Insulating enclosures around the receiver c. Wave trap d. RF stage 119. Which of the following stages in an FM receiver is responsible for drastically reducing the effect of static noise during the reception of a signal a. De-emphasis circuit

b. Mixer stage c. Squelch circuit d. Limiter stage 120. In most mixers, the oscillator frequency is ______ than the carrier frequency of the input signal. a. Higher b. Lower c. The same d. 10 kHz above 121. Features of a transmitter’s buffer stage include a. High stage b. Harmonic generation c. Improvement in frequency stability of the oscillator d. Low input impedance 122. What stage feeds the discriminator of an FM receiver? a. Local oscillator b. Mixer stage c. Final IF amplifier, which also acts as a limiter stage d. Buffer 123. In an FM receiver, the stage that has the IF signal is input and the audio signal output. a. Limiter b. Audio amplifier c. IF amplifier d. Discriminator 124. What is capture effect? a. All signals on a frequency are demodulated by an FM receiver b. The loudest signal received is the only demodulated signal c. All signals on a frequency are demodulated by an AM receiver d. The weakest signal received is the only demodulated signal 125. A double-sideband phone signal can be generated by a. Feeding a phase-modulated signal into a low-pass filter b. Modulating the plate voltage of a class-C amplifier c. Using a balanced modulator followed by a filter d. Detuning a Hartley oscillator 126. Pre-emphasis is used in FM transmitters to improve the signal-to-noise ratio of a. High modulating frequencies b. Low modulating frequencies c. All modulating frequencies d. Frequencies carrier 127. The result of cross-modulation is that a. The modulation of an unwanted signal is heard on the desired signal b. A decrease in modulation level of transmitted signals c. Of receiver quieting d. Of inverting sidebands in the final stage of the amplifier 128. Which of the following contains de-emphasis circuit?

a. b. c. d.

FM transmitter FM receiver VHF transmitter VHF receiver 129. Two AM transmitting antennas are close together. As a result the two modulated signals are mixed in the final RF stage of both transmitters. What is the resultant effect on other station? a. Harmonic interference b. Intermodulation interference c. Spurious interference d. Crossmodulation interference 130. The term used to refer to the reduction of receiver gain caused by the signal of a nearby station transmitter in the same frequency band? a. Quieting b. Cross-modulation interference c. Squelch gain rollback d. Desensitizing 131. What is the bandwidth occupied by the carrier, both sidebands and harmonics? a. Authorized bandwidth b. Bandwidth of emission and occupied bandwidth c. Operating bandwidth d. All of these 132. A class-C RF amplifier is collector amplitude modulated and its average dc level collector current does not change. This means a. A normal condition b. Excessive drive to the base c. Insufficient drive to the base d. Insufficient audio modulation 133. What determines the percentage modulation of an FM transmitter? a. Amplitude of the carrier b. Modulating frequency c. Carrier frequency d. Amplitude of the modulating signal 134. Deviation ratio of an FM transmitter is the ratio of the a. Maximum frequency swing to the highest modulating frequency b. Operating frequency of the assigned frequency c. Frequency swing to the modulating frequency d. Highest modulating frequency to the minimum frequency 135. The main purpose of the beat frequency oscillator (BFO) is to generate a. A 1 kHz not for Morse reception b. Aid in the reception of weak voice-modulated signals c. An output, whose frequency differs from the IF by 1 kHz d. A signal, whose frequency is the same as intermediate frequency 136. Normally, a linear class BRF power amplifier operates with a bias approximately equal to a. Twice cut-off

b. Ten times cut-off value c. 50% of cut-off value d. Projected cut-off 137. The purpose why an RF amplifier is operated under linear class-B conditions (as opposed to class-C) is to a. Generate only even harmonics b. Generate only odd harmonics c. Increase the efficiency d. Amplify of an AM signal 138. The term used to refer to the condition where the signal from a very strong station are superimposed on other signal being received. a. Cross-modulation interference b. Intermodulation distoriotion c. Receiver quieting d. Capture effect 139. In an FM-phone signal, ________ is the ratio between the actual frequency deviation to the maximum frequency deviation. a. FM compressibility b. Modulating index c. Percentage of modulation d. Quieting index 140. _______ is used to refer to the reception blockage of one FM-phone signal by another FM-phone signal. a. Capture effect b. Desensitization c. Cross-modulation interference d. Frequency discrimination 141. The receiver circuit that rids FM of noise is the a. Modulator b. Demodulator c. Limiter d. Low-pass filter 142.

The method of generating FM used by broadcasting station is Direct All of these Indirect Insertion 143. Deviation ratio of an FM transmitter is the ratio of the a. Maximum frequency swing to the highest modulating frequency b. Operating frequency of the assigned frequency c. Frequency swing to the modulating frequency d. Highest modulating frequency to the minimum frequency 144. A phase modulator has Kp= 2 rad/V. What RMS voltage of a sine wave would cause a peak phase deviation of 30 degrees? a. 0.158 V b. 0.185 V c. 0.518 V a. b. c. d.

d. 0.815 V In a phase-locked loop, VCO stands for a. Variable capacitor oscillator b. Varactor-capacitor oscillator c. Voltage-controlled oscillator d. VHF control oscillator 146. Which is a disadvantage of direct FM generation? a. The need for an AFC circuit b. The need for an AGC circuit c. Two balanced modulators are used d. The use of Class A amplifier which is very inefficient 147. Frequency division is useful in the implementation of a/an a. AM demodulator b. Frequency synthesizer c. AGC circuit d. FM demodulator 148. A particular synthesizer which contains only a single crystal is a. Direct b. Crystal-modulated c. Indirect d. Exact 149. Type of emission most affected by selective fading a. FM and DSB AM b. SSB and TV c. CCTV and CW d. CW and SSB 150. A system uses a deviation of 100 kHz and a modulating frequency of 15 kHz. What is the approximate bandwidth? a. 115 kHz b. 230 kHz c. 170 kHz d. 340 kHz 151. A quadrature detector requires that a. The inputs are coherent b. Four gates are provided c. The inputs are in phase d. The inputs are similar 152. Collector current in a class C amplifier is a. Sine wave b. Half-sine wave c. Pulse d. Square wave 153. The final power amplifier in an FM transmitter usually operates class a. A b. B c. C d. D 154. A phase-locked loop has a VCO with a free-running frequency of 14 MHz. As the frequency of the reference input is gradually raised from zero, the loop locks at 12 MHz and comes out of lock again at 18 MHz. Calculate the capture range. 145.

a. b. c. d.

4 MHz 2 MHz 12 MHz 8 MHz 155. If the frequency fed to the pre-amplifier of a basic transmitter with multipliers is composed of a pair of triplers and a doubler is 198 MHz, what frequency should the oscillator operate? a. 11 MHz b. 33 MHz c. 22 MHz d. 66 MHz 156. A phase-locked loop has a VCO with a free running frequency of 14 MHz. As the frequency of the reference input is gradually raised from zero, the loop locks at 12 MHZ and comes out of lock again at 18 MHz. Calculate the lock range. a. 4 MHz b. 2 MHz c. 12 MHz d. 8 MHz 157. A crystal oscillator is accurate within 0.0005%. How far off frequency could its output be at 37 MHz? a. 135 Hz b. 150 Hz c. 185 Hz d. 224 Hz 158. What is the term used to refer to the reception blockage of one FM-phone signal? a. Desensitization b. Cross-modulation interference c. Capture effect d. Frequency discrimination 159. How are FM phone signals detected? a. By a balanced modulator b. By a frequency discriminator c. By a product detector d. By a phase splitter 160. What is a frequency discriminator? a. A circuit for detecting FM signals b. A circuit for filtering two closely adjacent signals c. An automatic band switching circuit d. An FM generator 161. What is the term for the ratio between the largest tolerable receiver input signal and the minimum discernible signal? a. Intermodulation distortion b. Noise floor c. Noise figure d. Dynamic range 162. If the frequency spectrum of a signal has a bandwidth of 500 Hz with the highest frequency at 600 Hz, what should be the sampling rate according to the Nyquist theorem? a. 200 samples/sec b. 500 samples/sec c. 1000 samples/sec

d. 1200 samples/sec

MULTIPLE CHOICE QUESTIONS IN

ANGLE MODULATION Electronics Systems and Technologies By Melvin C. Arceo

ENCODED BY: SANTOLLO, Dan Alvin 1. He developed the first successful FM radio system a. B.E.Alpine b. N.S. Kapany c. E.H. Armstrong d. A.C.S. Van Heel 2. Results whenever the phase angle of sinusoidal wave is varied with respect to time a. angle modulation b. digital modulation c. amplitude modulation d. pulse modulation

3. In the spectrum of a frequency -modulated wave a. the carrier frequency disappears with a large modulation index b. the amplitude of any sideband depends on the modulation index c. the total number of sidebands depends on the modulation index d. the carrier frequency cannot disappear 4.What is the frequency swing of an FM broadcast transmitter when modulated 60% a. 60 kHz b. 45 kHz c. 30 kHz d. 25 kHz 5. Varying the frequency of a constant -amplitude carrier directly proportional to the amplitude to the modulating signal at a rate equal to the frequency of the modulating signal a. amplitude modulation b. angle modulation c. phase modulation d. frequency modulation 6. The amount of frequency deviation from the carrier center frequency in an FM transmitter is proportional to what characteristic of the frequency signal? a. amplitude b. frequency c. phase d. shape 7. It is a modulation where the angle of a wave carrier is varied from its reference value a. amplitude modulation b. angle modulation c. analog modulation

d. digital modulation 8. Both FM and PM are types of what kind of modulation? a. amplitude b. phase c. angle d. duty cycle 9. Varying the phase of a constant amplitude carrier displacement proportional to the amplitude of the modulating signal at a rate equal to the frequency of the modulating signal. a. amplitude modulation b. angle modulation c. phase modulation d. frequency modulation 10. The difference between phase and frequency modulation a. is purely theoretical because they are the same in practice b. is too great to make the two systems compatible c. lies in the poorer audio responses of phase modulation d. lies in the different definitions of the modulation index 11. The relative angular displacement of the carrier phase in radians with respect to the reference phase is called __________. a. phase deviation b. carrier deviation c. frequency deviation d. information deviation 12. If the amplitude of the modulating signal decreases, the carrier deviation a. increases b. decreases

c. remains constant d. goes to zero 13. On an FM signal, maximum deviation occurs at what point on the modulating signal? a. zero-crossing points b. peak positive amplitudes c. peak negative amplitude d. both peak positive and negative amplitudes 14. The amount of oscillator frequency increase and decrease around the carrier frequency is called _________. a. frequency deviation b. phase shift c. intelligence frequency d. baseband 15. The relative displacement of the carrier frequency in hertz in respect to its unmodulated value is called _____________. a. frequency deviation b. phase deviation c. information deviation d. carrier deviation 16. A pre-emphasis circuit provides extra noise immunity by a. boosting the bass frequencies b. amplifying the higher audio frequencies c. preamplfying the whole audio band d. converting the phase modulation to FM 17. It is the instantaneous change in phase of the carrier at a given instant of time and indicates how much phase of the carrier is changing with respect to its reference phase.

a. instantaneous frequency b. instantaneous frequency deviation c. instantaneous phase d. instantaneous phase deviation 18. Calculate the amount of frequency deviation caused by a limited noise spike that still cause an undesired phase shift of 35 degrees when the input frequency is 5kHz. a. 2.40kHz b. 3.05kHz c. 1.29kHz d. 4.45kHz 19. Which of the following determines the rate of carrier deviation? a. intelligence frequency b. frequency deviation c. carrier frequency d. broadband frequency 20. It is the precise phase of the carrier at a given instant of time a. instantaneous phase deviation b. instantaneous phase c. instantaneous frequency deviation d. instantaneous frequency 21. In PM, a frequency shift occurs while what characteristic of the modulating signal is changing? a. shape b. phase c. frequency d. amplitude

22. In FM, it is a device that in which amplitude variations are derived in response to frequency or phase variations a. detector b. discriminator c. demodulator d. receiver 23. Maximum frequency deviation of a PM signal occurs at a. zero-crossing points b. peak positive amplitudes c. peak negative amplitude d. peak positive and negative amplitude 24. Since noise phase-modulates the FM wave, as the noise sideband frequency approaches the carrier frequency, the noise amplitude a. remains constant b. is decreased c. is increased d. is equalized 25. It is the instantaneous change in frequency of the carrier and is defined as the first time derivative of the phase deviation a. instantaneous frequency b. instantaneous frequency deviation c. instantaneous phase d. instantaneous phase deviation 26. Since noise phase- modulates the FM wave, as the noise sideband frequency approaches the carrier frequency, the noise amplitude a. remains constant b. is decreased

c. is increased d. is equalized 27. It is the precise frequency of the carrier at a given instant of time is defined as the first time derivative of the instantaneous phase. a. instantaneous frequency b. instantaneous frequency deviation c. instantaneous phase d. instantaneous phase deviation 28. It is the output-versus-input transfer functions for modulators which give the relationship between the output parameter changes in respect to specified changes in the input signal. a. frequency deviation b. deviation sensitivity c. transconductance curve d. phase deviation 29. When the modulating frequency is doubled, the modulation index is halved, and the modulating voltage remains constant. The modulation system is a. amplitude modulation b. phase modulation c. frequency modulation d. any of the above 30. In PM, carrier frequency deviation is not proportional to: a. modulating signal amplitude b. carrier amplitude and frequency c. modulating signal frequency d. modulator phase shift 31. To compensate for increases in carrier frequency deviation with an increase in modulating signal frequency, what circuit is used between the modulating signal and phase modulator?

a. low-pass filter b. high-pass filter c. phase shifter d. bandpass filter 32. Indicate which one of the following is not an advantage of PM over AM: a. better noise immunity is provided b. lower bandwidth is required c. the transmitted power is more useful d. less modulating power is required 33. With phase modulation, the maximum frequency deviation occurs during what value of the modulating signal? a. positve peak value b. rms value c. negative peak value d. zero crossings 34. With frequency modulation, maximum frequency deviation occurs _____ of the modulation signal. a. positive peak value b. both positive and negative peak value c. negative peak value d. zero crossings 36. With phase modulation, peak phase deviation is called _________. a. modulation index b. frequency deviation c. phase deviation d. instantaneous phase

37. The FM produced by PM is called a. FM b. PM c. indirect FM d. indirect PM 38. In a broadcast superheterodyne receiver, the a. local oscillator operates below the signal frequency b. mixer input must be tuned to the signal frequency c. local oscillator frequency is normally double the OF d. RF amplifier normally works at 455kHz above the carrier frequency 39. If the amplitude of the modulating signal applied to a phase modulator is constant, the output signal will be a. zero b. the carrier frequency c. above the carrier frequency d. below the carrier frequency 40. To prevent overloading of the last IF amplifier in the receiver, one should use the a. squelch b. variable sensitiivity c. variable selectivity d. double conversion 41. The peak-to-peak frequency deviation is sometimes called __________. a. phase deviation b. peak phase deviation c. carrier swing

d. instantaneous frequency 42. A 100MHz carrier is deviated 50 kHz by 4kHz signal. The modulation index is a. 5 b. 8 c. 12.5 d. 20 43. With angle modulation, it is defined as the ratio of the frequency deviation actually produced to the maximum frequency deviation allowed by law stated in percent form. a. modulation index b. percent modulation c. frequency deviation d. phase deviation 44. In a broadcast FM system, the input S/N = 4. Calculate the worst case S/N at the output if the receiver's internal noise effect is negligible. a. 19.8:1 b. 21.6:1 c. 23:1 d. 15:1 45. It is a circuit in which the carrier is varied in such a way that its instantaneous phase is proportional to the modulating signal. a. frequency modulators b. amplitude modulators c. phase modulators d. mixers 46. In a ratio detector a. the linearity is worse than in a phase discriminator

b. stabilization against signal strength variations is provided c. the output is twice that obtainable from the similar phase discriminator d. the circuit is the same as in a discriminator, except that the diodes are reversed 47. The maximum deviation of an FM carrier is 2kHz by a maximum modulating signal of 400Hz. The deviation ratio is a. 0.2 b. 5 c. 8 d. 40 48. The unmodulated carrier is a single-frequency sinusoid commonly called _________. a. unrest frequency b. rest frequency c. frequency-modulated frequency d. carrier frequency 49. It is a circuit in which the carrier is varied in such a way that its instantaneous phase is proportional to the integral of the modulating signal a. phase modulator b. phase deviator c. amplitude deviator d. frequency modulator 50. The typical squelch circuit a. cuts off an audio amplifier when the carrier is absent b. eliminates the RF interference when the signal is weak c. cuts off an IF amplifier when the AGC is maximum d. cuts off an IF amplifier when the AGC is minimum 51. Frequency modulators are also known as _________.

a. phase deviators b. frequency deviators c. phase modulators d. amplitude deviators 52. A 70 kHz carrier has a frequency deviation of 4 kHz with a 1000Hz signal. What is the bandwidth of the FM signal? a. 4kHz b. 7kHz c. 10 kHz d. 28 kHz 53. The controlled oscillator synthesizer is sometimes preferred to the direct one because a. it is simpler piece of equipment b. its frequency stability is better c. it does not require crystal oscillators d. it is relatively free of spurious frequencies 54. A system with a differentiator followed by an FM modulator is called a. PM modulator b. FM modulator c. PM demodulator d. FM demodulator 55. The image frequency of a superheterodyne receiver a. is created within the receiver itself b. is due to insufficient adjacent channel rejection c. is not rejected by the IF tuned circuits d. is independent of the frequency to which the receiver is tuned

56. A system with FM demodulator followed by an integrator a. PM modulator b. PM demodulator c. FM modulator d. FM demodulator 57. A system with an integrator followed by a PM modulator a. PM modulator b. FM modulator c. PM demodulator d. FM demodulator 58. An FM transmitter has a maximum deviation of 12kHz and a maximum modulating frequency of 12 kHz. The bandwidth by Carson's rule is a. 24kHz b. 33.6kHz c. 38.8kHz d. 48kHz 59. A system with PM demodulator followed by a differentiator a. PM modulator b. FM modulator c. PM demodulator d. FM demodulator 60. A receiver has poor IF selectivity. It will therefore also have poor a. blocking b. double-spotting c. diversity reception

d. sensitivity 61. Three point tracking is achieved with a. variable selectivity b. the padder capacitor c. double spotting d. double conversion 62. He mathematically proved that for a given modulating signal frequency a frequencymodulated wave cannot be accommodated in a narrower bandwidth than an amplitude modulated wave. a. R.C. Alpine b. E.H. Armstrong c. J.R. Carson d. J.J. Thomson 63. The maximum allowed deviation of the FM sound signal in TV is 25 kHz. If the actual deviation is 18kHz, the percent modulation is a. 43 percent b. 72 percent c. 96 percent d. 139 percent 64. The local oscillator of a broadcast receiver is tuned to a frequency higher than the incoming frequency a. to help the image frequency rejection b. to permit easier tracking c. because otherwise an intermediate frequency could not be produced d. to allow adequate frequency coverage without switching 65. Which of the following is not a major benefit of FM over AM? a. greater efficiency

b. noise immunity c. capture effect d. lower complexity and cost 66. Low-index FM systems are also known as __________. a. wideband FM b. narrowband FM c. commercial FM d. medium FM 67. For high-index signal, a method of determining the bandwidth is called ________ approach a. quasi-stationary b. quasi-movement c. quasi-deviation d. any of these 68. When a receiver has a good blocking performance, this means that a. it does not suffer from double-spotting b. its image frequency rejection is poor c. it is unaffected by AGC derived from a nearby transmission d. its detector suffers from burnout 69. He established a general rule to estimate the bandwidth for all angle-modulated system regardless of the modulation index. a. R.C. Alpine b. E.H. Armstrong c. J.R. Carson d. J.J. Thomson 70. An AM receiver uses a diode detector for demodulation. This enables it satisfactority to receive

a. single-sideband, suppressed carrier b. single-sideband, reduced carrier c. independent sideband d. single-sideband, full carrier 71. The primary disadvantage of FM is its a. higher cost and complexity b. excessive use of spectrum space c. noise susceptibility d. lower efficiency 72. A rule that approximates the bandwidth necessary to transmit an angle-modulated wave as twice the sum of the peak frequency deviation and the highest modulating frequency. a. Carson's rule b. Shannon's rule c. Hartley's law d. Hartley-Shannon law 73. It is the worst case modulation index and is equal to the maximum peak frequency deviation divided by the maximum modulating signal frequency a. peak phase deviation b. frequency deviation c. deviation ratio d. signal to noise ratio 74. The receiver circuit that rids FM noise is the a. modulator b. demodulator c. limiter d. low-pass filter

75. The phenomenon of a strong FM signal dominating a weaker signal on a common frequency is referred to as the a. capture effect b. blot out c. quieting factor d. domination syndrome 76. The highest side frequencies form one channel are allowed to spill over into adjacent channels producing an interference known as _________. a. co-channel interference b. adjacent channel interference c. splatter d. overmodulation 77. A pre-emphasis is usually a ________. a. high-pass filter b. band-stop filter c. low-pass filter d. bandpass filter 78. Frequency modulation transmitters are more efficient because their power is increased by what type of amplifier? a. class A b. class B c. class C d. all of the above 79. Noise interferes mainly with modulating signals that are a. sinusoidal b. non-sinusoidal

c. low frequencies d. high frequencies 80. A de-emphasis is usually a _________. a. high pass filter b. band-stop filter c. low-pass filter d. bandpass filter 81. A pre-emphasis is a __________. a. integrator b. differentiator c. either integrator or differentiator d. neither integrator or differentiator 82. A de-emphasis is a _____________. a. integrator b. differentiator c. either integrator or differentiator d. neither integrator or differentiator 83. Pre-emphasis circuit boost what modulating frequencies before modulation? a. high frequencies b. mid-range frequencies c. low frequencies d. all of the above 84. The primary disadvantage of direct PM a. relatively unstable LC oscillators must be used to produce carrier frequency which prohibits using crystal oscillators

b. relatively high frequency deviations and modulation indices are easily obtained due to the fact that the oscillators are inherently unstable. c. crystal oscillators are inhrently stable and therefore more difficult for them to achieve high phase deviations and modulation indices d. carrier oscillator is isolated form the actual modulator circuit and therefore can be stable source. 85. It is an angle modulation in which the frequency of the carrier is deviated by the modulating signal a. direct PM b. PM c. indirect FM d. any of these 86. One of the following is a method of performing frequency up conversion a. heterodyning b. amplification c. modulation d. none of these 87. A pre-emphasis circuit is a a. low-pass filter b. high-pass filter c. phase shifter d. bandpass filter 88. Pre emphasis is compensated for the receiver by a a. phase inverter b. bandpass filter c. high-pass filter d. low-pass filter

89. A circuit that compares the frequency of the noncrystal carrier oscillator to a crystal reference oscillator and then produces a correction voltage proportional to the difference between the two frequencies a. AFC b. squelch circuit c. AGC d. heterodyning circuit 90. A frequency selective device whose output voltage is proportional to the difference between the input frequency and its resonant frequency a. modulator b. squelch circuit c. frequency discriminator d. FM transmitters 91. Allows FM receiver to differentiate between two signals received with the same frequency but different amplitudes a. flywheel effect b. amplitude limiting c. noise immunity d. capture effect 92. If an FM transmitter employs one doubler, one tripler, and one quadrupler, what is the carrier frequency swing when the oscillator frequency swing is 2kHz? a. 24 kHz b. 48 kHz c. 14 kHz d. 12 kHz 93. The cut-off frequency of pre-emphasis and de-emphasis circuits is a. 1 kHz

b. 2.122 kHz c. 5 kHz d. 75 kHz 94. Which of the following is not a disadvantage of angle modulation? a. wide bandwidth b. complex c. high cost d. less noise 95. In FM receivers, which of the following rejects the image frequency? a. preselector b. detector c. IF amplifier d. mixer 96. In FM receivers, which of the following provides most gain and selectivity of the receiver? a. detector b. RF amplifier c. local oscillator d. IF amplifier 97. Another name for Voltage Variable Capacitor is a. PIN diode b. varactor diode c. snap diode d. hot carrier diode 98. The depletion region in a junction diode forms what part of a capacitor? a. plates

b. leads c. package d. dielectric 99. Which of the following removes the information from the modulated wave in FM receivers? a. amplifiers b. mixer c. speakers d. discriminator 100. The final IF amplifier in FM receivers is sometimes called ___________. a. tuned amplifier b. limiter c. passband filter d. any of these 101. _________ are frequency-dependent circuits designed to produce an output voltage that is proportional to the instantaneous frequency at its output a. PM receivers b. PM demodulators c. FM demodulators d. FM receivers 102. Increasing the reverse bias on a varactor diode will it cause its capacitance to a. decrease b. increase c. remains the same d. drop to zero 103. The capacitance of a varactor diode is in what general range?

a. pF b. nF c. uF d. F 104. Which of the following is the simplest form of tuned-circuit frequency discriminator? a. Foster-Seeley discriminator b. Ratio detector c. slope detector d. PLL detector 105. It is simply two single-ended slope detectors connected in parallel and fed 180 degrees out phase. a. Foster-Seeley discriminator b. quadrature detector c. balanced slope generator d. PLL detector 106. The frequency change in crystal oscillator produced by a varactor diode is a. zero b. small c. medium d. large 107. A phase modulator varies the phase shift of the a. carrier b. modulating signal c. modulating voltage d. sideband frequency

108. Which of the following tuned-circuit frequency discriminator is relatively immune to amplitude variations in its input signal? a. ratio detector b. slope detector c. balanced slope detector d. quadrature detector 109. In FM demodulators, it is also called coincidence detector a. quadrature demodulator b. PLL demodulator c. Foster-Seely discriminator d. ratio detector 110. The widest phase variation is obtained with ________. a. RC low-pass filter b. RC high-pass filter c. LR low-pass filter d. LC resonant circuit 111. An FM receiver provides 100dB of voltage gain prior to the limiter. Calculate the receiver's sensitivity if the limiter's quieting for an FM receiver is 300mV? a. 4.5 uV b. 3.0 uV c. 2.1 uV d. 1.3 uV 112. The small frequency change produced by a phase modulator can be increased by using ___________. a. amplifier b. mixer

c. frequency multiplier d. frequency divider 113. In FM receiver, limiters produce a constant-amplitude output of all signals above a prescribed minimum input level called _________. a. threshold voltage b. capture level c. quieting level d. any of these 114. The inherent ability of FM to diminish the effects of interfering signals is called _______. a. capture effect b. noise suppression c. adjacent channel rejection 115. A crystal oscillator whose frequency can be changed by an input voltage is called _______. a. VCO b. VXO c. VFO d. VHF 116. Which oscillators are preferred for carrier generators because of their good frequency stability? a. LC b. RC c. LR d. crystal 117. Which of the following frequency demodulators requires an input limiter? a. Foster-Seely discriminator b. Pulse-averaging discriminator

c. quadrature detector d. PLL 118. Provides a slight automatic control over the local oscillator circuit and compensates for its drift that would otherwise cause a station to become detuned. a. AGC b. AFC c. VVC d. VCO 119. ________ of an FM receiver is the maximum dB difference signal strength between two received signals necessary for the capture effect to suppress the weaker signal. a. capture effect b. capture gain c. capture ratio d. capture loss 120. When two limiter stages are used, there is called ___________. a. double limiting b. two-time limiting c. reserve limiting d. ratio limiting 121. Which discriminator averages pulses in a low-pass filter? a. ratio detector b. PLL c. quadrature detector d. pulse-averaging discriminator 122. Which of the frequency demodulator is considered the best overall? a. ratio detector

b. PLL c. quadrature d. pulse-averaging discriminator 123. One of the prominent advantage of FM over PM is a. FM requires frequency multipliers to increase the modulation index and frequency deviation to useful levels b. the voltage controlled oscillators of FM can be directly modulated and produce outputs with high frequency deviations and high modulation c. the modulation index of FM is independent of the modulating signal frequency d. FM offers better signal-to-noise performance than PM 124. What special speaker is used for low frequency? a. baffle b. base c. tweeter d. woofer 125. Each speaker assembly at the receiver reproduces exactly the same information a. monophonic b. multiphonic c. stereophonic d. any of these 126. In a pulse averaging discriminator, the pulse are produced by a(n) a. astable multivibrator b. zero-crossing detector c. one-shot d. low-pass filter 127. A reactance modulator looks like a capacitance of 35pF in parallel with the oscillator-tuned

circuit whose inductance is 50 uH and capacitance is 40 pF. What is the center frequency of the oscillator prior to FM? a. 1.43 MHz b. 2.6 MHz c. 3.56 MHz d. 3.8 MHz 128. The frequency of an SCA channel subcarrier is _______. a. 38 kHz b. 15 kHz c. 67 kHz d. 53 kHz 129. The L-R stereo channel in FM broadcasting is between a. 50 Hz to 15 kHz b. 60 kHz to 74 kHz c. 23 kHz to 53 kHz d. 20 Hz to 20 kHz 130. An FM demodulator that uses a differential amplifier and tuned circuits to convert frequency variations into voltage variations is the a. quadrature detector b. Foster-Seeley discriminator c. differential peak detector d. phase-locked loop 131. The output amplitude of the phase detector in a quadrature detector is proportional to a. pulse width b. pulse frequency c. input amplitude

d. the phase shift value at center 132. The output to a PLL is 2MHz. In order for the PLL to be locked. The VCO output must be a. 0 MHz b. 1 MHz c. 2 MHz d. 4 MHz 133. With stereo transmission, the maximum frequency deviation is a. 75 kHz b. 15 kHz c. 25 kHz d. 3 kHz 134. The L + R stereo channel occupies _________. a. 50 Hz to 15 kHz b. 60 kHz to 74 kHz c. 23 kHz to 53 kHz d. 20 Hz to 20 kHz 135. The band of frequencies over which a PLL will acquire or recognize an input signal is called the a. circuit bandwidth b. capture range c. band of acceptance d. lock range 136. The three primary frequency bands are allocated by FCC for two-way FM radio communications except: a. 132 MHz to 174 MHz b. 450 MHz to 470 MHz

c. 806 MHz to 947 MHz d. 1026 MHz to 1035 MHz 137. The maximum frequency deviation for two-way transmitters is typically a. 25 kHz b. 5 kHz c. 75 kHz d. 3 kHz 138. Decreasing the input frequency to be locked PLL will cause the VCO output to a. decrease b. increase c. remains constant d. jump to the free-running frequency 139. The range of frequencies over which a PLL will track input signal variations is known as the a. circuit bandwidth b. capture range c. band of acceptance d. lock range 140. The maximum modulating signal frequency for two-way transmitter is typically a. 3 kHz b. 5 kHz c. 15 kHz d. 75 kHz 141. Over a narrow range of frequencies, the PLL acts like a a. low-pass filter b. bandpass filter

c. tunable oscillator d. frequency modulator 142. The output of a PLL frequency demodulator is taken from the a. low-pass filter b. VCO c. phase detector d. none of these 143. The primary advantage of FM over AM a. capture effect b. noise immunity c. FM can use class C amplifiers d. FM is more efficient 144. The usual cutoff frequency of pre-emphasis and de-emphasis in broadcast FM? a. 50 Hz b. 75 Hz c. 2122 Hz d. 3183 Hz 145. The maximum deviation for narrowband FM? a. 2500 b. 5 c. 1.67 d. 75 146. Which of the following is best frequency demodulator in use? a. Foster-Seeley discriminator b. ratio detector

c. slope detector d. PLL 147. The range of frequencies over which the PLL will capture an input signal is known as ________. a. lock range b. capture range c. bandwidth d. sidebands 148. Type of FM demodulator that is widely used in TV audio demodulators a. ratio detector b. quadrature detector c. PLL d. pulse-averaging discriminator 149. A variation of Foster-Seeley discriminator widely used in oldr TV receiver designs a. ratio detector b. PLL c. quadrature detector d. crosby modulator 150. The range of frequencies over which a PLL will track an input is called a. lock range b. capture range c. track range d. driving range 151. What is the maximum deviation for monoaural TV sound a. 25 kHz

b. 75 kHz c. 50 kHz d. 125 kHz 152. What is the maximum deviation for stereo TV sound? a. 25 kHz b. 75 kHz c. 50 kHz d. 125 kHz 153. In FM stereo broadcasting, the L + R signal a. double-sideband modulates a subcarrier b. modulates the FM carrier c. frequency modulates a subcarrier d. is not transmitted 154. In FM stereo broadcasting, the L - R signal a. double-sideband modulates a subcarrier b. modulates the FM carrier c. frequency modulates a subcarrier 155. The SCA signal if used in FM broadcasting is transmitted via a. a 19 kHz subcarrier b. a 38 kHz subcarrier c. a 67 kHz subcarrier d. the main FM carrier 156. Which of the following is considered as an indirect method of generating FM? a. reactance modulator b. balanced modulator

c. varactor diode modulation d. armstrong system 157. In an FM system, if the modulation index is doubled by halving the modulating frequency, what will be the effect on the maximum deviation? a. remains the same b. doubles c. decrease by 1/2 d. increase by 1/4 158. Determine from the following the common use of DSB in broadcast and telecommunication. a. satellite communications b. FM/TV stereo c. two-way communications d. telephone systems 159. Phase modulation emission type a. F3F b. G3E c. F3E d. F3C 160. The range of frequencies over which a PLL will cause the input of the VCO signals to remain synchronized is known as the _________ range. a. capture b. lock c. acquisition d. any of these 161. If the PLL input is zero, the VCO will operate at its ____________ frequency.

a. free-running b. natural c. operating d. any of these 162. Since a PLL will only respond to signals over a narrow frequency range, it acts likes a ________. a. low-pass filter b. high-pass filter c. bandpass filter d. bandstop filter 163. In a PLL demodulating an FM signal, the VCO output is an exact reproduction of the ___________. a. modulating signal b. carrier signal c. carrier amplitude d. VCO output 164. In a PLL demodulating an FM signal, the VCO output is an exact reproduction of the ________. a. FM input b. VCO input c. modulating signal d. error signal 165. After the IF stages have been aligned, the next state to align in FM receiver is a. local oscillator b. limiter stage c. RF amplifier

d. mixer stage 166. The modulation system used for telegraphy is a. frequency-shift keying b. two-tone modulation c. purse-code modulation d. single-tone modulation 167. What is emission F3F? a. Facsimile b. RTTY c. modulated CW d. television 168. What is a frequency discriminator? a. a circuit for filtering two closely adjacent signals b. a circuit for detecting FM signals c. an FM generator d. an automatic bandswitching circuit 169. Type of radio communication transmission utilizing frequency modulation technique a. television video b. broadcasting in 535-1606 kHz c. single sideband HF transmission d. television audio 170. Why was FM first developed? a. to compete with AM b. to overcome noise c. to increase listeners

d. to supplement AM 171. To what feature of the modulating tone is FM deviation proportional? a. amplitude b. frequency c. phase d. phase shift 172. Which of the following is not a basic filed of FM? a. broadcast b. TV video c. mobile communications d. amateur radio 173. Under what condition would a 1 kHz AF signal produce a single pair of FM sidebands? a. wideband b. broadcast FM c. TV audio FM d. narrowband FM 174. What deviation is considered 100% for FM broadcast stations? a. 75 kHz b. 220 kHz c. 270 kHz d. 75 kHz or 220 kHz 175. In FM broadcasting, what is the highest required modulating frequency? a. 75 kHz b. 50 kHz c. 25 kHz

d. 15 kHz 176. In FM broadcasting, what is the lowest required modulating frequency? a. 50 Hz b. 30 Hz c. 10 Hz d. 5 Hz 177. What is the disadvantage of slope detection of FM> a. no discrimination against noise b. less AF distortion c. less AF out d. no filtering of carrier 178. What is the unction of the dc that comes out of the dc amplifier in a PLL-type FM detector? a. carrier signal b. filter signal c. error signal d. phase signal 179. What is the function of the dc that comes out of the dc amplifier in a PLL-type FM detector? a. oscillators b. AF signal c. RF signal d. carrier signal 180. Why should discriminators be tuned for a straight characteristic S-curve? a. less AF distortion b. greater AF out

c. less RF out d. less RF distortion 181. What band for high-Q coils be more desirable for stagger-tuned-type discriminator transformer? a. wide b. intermediate c. interfacing d. narrow 182. In a Foster-Seeley circuit, the AF output voltage is ________. a. varying DC b. varying AC c. steady DC d. steady AC 183. In a stagger-tuned discriminator, the AF output voltage is _________. a. varying DC b. varying AC c. steady DC d. steady AC 184. In a ratio detector, the AF output voltage is a. steady AC b. varying AC c. steady DC d. varying DC 185. In a gated-beam detector, the AF output voltage is _________. a. steady DC b. varying AC

c. varying DC d. steady AC 186. Which of the following discriminator circuits require limiters ahead of them? a. quadrature detector b. foster-seeley discriminator c. slope detector d. stagger-tuned 187. Which of the following discriminator circuits provide an automatic gain control voltage? a. ratio detector b. balanced slope detector c. quadrature detector d. stagger-tuned detector 188. Which of the following discriminator circuits has its diodes in series? a. ratio b. quadrature detector c. round-travis detector d. slope detector 189. To what frequency must the gated-beam quadrature circuit be tuned in a TV receiver? a. 10.7 MHz b. 455 kHz c. 70 MHz d. 4.5 MHz 190. To what frequency must the gated-beam quadrature circuit be tuned in an FM broadcast receiver? a. 4.3 MHz

b. 10.7 MHz c. 11 MHz d. 4.8 MHz 192. With what FM detectors would AGC be an advantage? a. foster-seeley detector b. ratio detector c. quadrature detector d. phase-locked loop 193. What is the reason for using pre-emphasis? a. increase amplitude b. reduce carrier shift c. amplify RF signal d. reduce noise reception 194. What are the two types of stages in an FM receiver that differ from those in an AM receiver? a. limiting IF and detectors b. oscillators and IF amplifiers c. mixers and RF amplifiers d. local oscillators and mixers 195. What special circuits are used in a squelch system that can follow changing noise levels? a. noise amplifiers b. rectifier c. dc amplifier d. any of these 196. Why might FM be better than AM for mobile ________.

a. better coverage b. not affected by solar cycles c. reduce flutter d. not absorbed by ionosphere 197. What is the order of circuit alignment in an FM receiver? a. discriminator, limiters, IF, mixer and RF b. RF, limiters, IF, mixer and discriminator c. limiters, mixer, RF, discriminator and IF d. RF, mixer, RF, IF, limiters and discriminator 198. What is the another name for the reactance-tube modualtor? a. Crosby b. Foster-Seeley c. Round Travis d. Messier 199. What effect would be produced if a small inductance were used in plasce of the 50 pF capacitance in the reactance-tube modulator? a. the circuit becomes resistive b. reactance modulator looks like an inductive circuit c. reactance modulator looks like Xc d. any of these 200. The following are significant circuits in the AFC system except: a. crystal b. mixer c. IF d. filter

201. Besides the reactance-tube modulator, what is another method of producing direct FM? a. armstrong modulator b. voltage variable capacitor c. impeadance modulator d. slug indicator 202. What is the advantage of PM? a. can use crystal oscillator b. uses more multistage c. less selective fading d. simplicity 203. What was the first broadcast FM system called? a. Arc transmitter b. MOPA c. Armstrong d. crystal 204. Why are limtiers used in FM transmitters? a. any of these b. clip noise peaks c. prevent overdrive of discriminators d. prevent overdeviation 205. Why are limiters used in FM receivers? a. provide better noise performance b. clip noise peaks c. prevent overdrive of discriminators d. any of these

206. What signals might feed into an FM broadcast station audio control console? a. microphones b. turntables c. remote lines d. any of these

Moduloation/Demodulation 1. A method that applied the modulated wave to the vertical deflection circuit of the oscilloscope and the modulating signal to the horizontal deflection circuit. a. Trapezoidal method b. Circular method c. Square method d. Any method 2. The heart of all methods of single-sideband modulation and demodulation a. Modulator b. Balanced modulator c. Modulation d. demodulation 3. If the frequency and phase are parameters of carrier angle, which is a function of time, the general term ___________-cover both. a. Amplitude modulation b. Frequency modulation c. Phase modulation d. Angle modulation 4. In FM radio communication system, narrow-band (NBFM) is used rather than wideband (WBFM), because it, a. Improves signal to noise ration b. Reduces interchannel interference c. Provides maximum coverage for a given amount of power d. All of the above 5. Radio transmitter basically consists of two principal parts, one reproducing a carrier frequency and one for __________. a. IF Frequency b. RF Frequency c. Modulating Frequency d. Power 6. Is a measure of its ability to maintain as nearly a fixed frequency as possible over as long as time interval as possible. a. Receiver Noise Factor b. Selectivity

c. Sensitivity d. Frequency stability 7. Is the effect of two-transmitter when they are in close proximity. This results into the sum and difference frequencies of two carriers. a. Intermodulation effect b. Intermodulation interference c. Intermodulation product d. intermodulation 8. _________ is a continuous frequency capable of being modulated or impressed with a second information carrying signal. a. Carrier frequency b. Center frequency c. IF frequency d. RF frequency 9. The varactor diode used in FM may be represented by the approximate equivalent circuit of the _____ in series with a ________. a. Diode, capacitor b. Diode, resistor c. Capacitor, resistor d. Any of these 10. The name varactor comes from variable _________. a. Resistor b. Capacitor c. Diode d. reactor 11. 75 microseconds pre-emphasis time is used in __________. a. FM b. AM c. TV d. None of these 12. Recovers the modulating voltage from the frequency modulation by utilizing the phase angle shift between primary and secondary voltages of tuned oscillators. a. Direct method b. Indirect method c. Foster-Seeley discriminator d. Slope detector 13. Is used in FM receivers to “lock onto” the received signal and stabilized recetions. a. Automatic Gain Control b. Automatic Frequency Control c. Muscle Control d. Automatic Frequency Gain Control 14. Are amplifier circuits that are used to eliminate amplitude modulation and amplitudemodulated noise from received FM Signals before detection. a. Demodulators b. Diode detector c. Amplitude limiters

d. None of these 15. If the total sideband power is 12.5% of the total radiated power, find the modulation index. a. 50 percent b. 53.4 percent c. 26.2 percent d. 32.3 percent 16. Carriers are spaced at 20 kHz, beginning at 100 kHz. Each carrier is modulated by a signal with a 5 kHz bandwidth. Is there interference from the sideband? a. Yes b. No c. Maybe d. Secret 17. For an unmodulated carrier of 150 V and a modulated peak value of 230 V. What is the modulation index a. 0.35 b. 0.533 c. 0.652 d. 0.42 18. New frequencies outside the regular AM spectrum are called ___________. a. Distortion b. Interference c. Splatter d. Harmonic 19. A DSB-SC has a total power of 350 watts with 100% modulation suppresses 50% of the carrier, and the suppressed carrier power goes to the sidebands. How much power is in the sidebands? a. 116.67 W b. 233.33 W c. 175 W d. 350 W 20. A DSB-SC system must suppress the carrier by 30 dB from its original value of 30 W. What value must the carrier be reduced? a. 30000 W b. 0.03 W c. 300 W d. 0.003 W 21. ___________, which further amplifies the signal and has the bandwidth and passband shaping appropriate for the received signal. a. RF stage b. Mixer and local oscillator stage c. IF stage d. AF stage 22. In FM, a bandwidth estimate 98 percent level of Bessel functions a. Approximate bandwidth

b. Narrow-band Bandwidth c. Carson’s rule d. Wideband bandwidth 23. The complete series of stages for reproducing the FM signal with the desired carrier and deviation is the _______. a. Modulator b. Exciter c. IF stage d. RF stage 24. Is the ability of FM system to provide low-noise, high fidelity music background/broadcast.. a. Monophonic b. Stereophonic c. Stereonic d. SCA 25. It make use of the shape of IF filter frequency response roll-off versus frequency. a. Foster Seeley b. Slope detector c. Diode detector d. Quadrature detector 26. In AM, modulation index is a number lying between ____ and 1. a. 2 b. 5 c. 0 d. 3 27. This form of modulation is also known as independent sideband emission. a. A3E b. R3E c. H3E d. B8E 28. An attenuated carrier is reinserted into the SSB signal to facilitate receiver tuning and demodulation. a. A3E b. R3E c. H3E d. B8E 29. Standard AM used for broadcasting a. A3E b. R3E c. H3E d. B8E 30. Single sideband, suppressed carrier in which the carrier is suppressed by at least 45 dB in the transmitter. a. A3E b. R3E c. H3E

d. B8E 31. The shift in the carrier frequency from the resting point compared to the amplitude of the modulating signal is called _______. a. Index b. Deviation ratio c. Carrier frequency d. Deviation frequency 32. In FM, the amplitude of the modulated frequency wave remains ___________ at all times. a. Varying b. Dependent c. Constant d. variable 33. An AM has a maximum span of 30 V, what is the required minimum span to attain 100% modulation? a. 30 V b. 20 V c. 0 V d. None of these 34. DZMM having a carrier frequency of 630 kHz is modulated by 2.6 kHz audio signal having an amplitude of 37.5 V. What is the amplitude voltage of 630 kHz carrier frequency at 0.35 modulation index? a. 57.6 V b. 107.14 V c. 206.5 V d. 86.2 V 35. If the sideband power is 50% of the carrier power, what is the modulation index? a. 50% b. 75% c. 90% d. 100% 36. If the increase power is 180 watts at 1 kW unmodulated output power the modulation index is _________. a. 75% b. 60% c. 50% d. 25% 37. In AM, if the unmodulated power carrier is 10 kW, and the total power is 15 kW, what is the upper sideband power at 100% modulation index? a. 25 kW b. 2 kW c. 2.5 kW d. 4 kW 38. If the input resistance of the base station of AM broadcast produced 20 kW carrier power, at what modulation index should the antenna rise at 108.63 A?

a. 20% b. 50% c. 60% d. 80% 39. ________ used a phase detector to compare the phase and frequency of the received signal to the VCO output. a. PIL b. PAL c. PLL d. PLI 40. A filter with a roll-off of 6 dB/kHz is used as a slope detector. The input signal varies with +3 kHz deviation from center carrier frequency. How many dB down is the output at full deviation? a. 9 dB b. -18 dB c. 18 dB d. -9 dB 41. A receiver limiter requires a 20 mV signal for quieting operation. The voltage gain between the RF input and the limiter is 57.7 dB, what is the input at the antenna terminal assuming equal resistance? a. 75.6 mV b. 26.67 uV c. 52.3 uV d. 49.6 uV 42. A 1-MHz carrier is modulated with a resulting 100 Hz deviation. It undergoes x36 multiplication, followed by mixing with a 34.5 MHz signal and remultiplication by 72. What is the final carrier and deviations? a. 5076 MHz, ± 2592 MHz b. 2592 MHz, ± 259.2 kHz c. 2592MHz, ± 5076 MHz d. 259.2 MHz, ± 108 kHz 43. For standard commercial broadcast FM, the deviation ratio is ________. a. 15 b. 75 c. 5 d. 10 44. A system has 150 kHz of bandwidth available for 10 kHz modulation signal. What is the approximate deviation to be used? a. 35 kHz b. 65 kHz c. 25 kHz d. 15 kHz 45. An FM has a deviation of 100 kHz and a modulating frequency of 15 kHz, what happen to m if the deviation triples? a. 6.66

b. 2.22 c. 4.12 d. 0.20 46. A receiver for a signal at 100 MHz uses a 10.7 MHz IF and low tracking. What is the image frequency? a. 89.3 MHz b. 78.6 MHz c. 52.5 MHz d. 35.2 MHz 47. What is the change in resonant frequency of the actual varactor capacitance value differs by -5% (0.05) of the nominal value? a. 2.06 b. 3.02 c. 1.03 d. 5.06 48. An oscillator resonate at 1 MHz with a nominal 100 pF capacitor and 0.25 mH inductor, what s the resonant frequency of the actual capacitor value is +20% of the nominal value? a. 1.006 MHz b. 0.9188 MHz c. 3.625 MHz d. 2.00123 MHz 49. “Front end” is also called _________. a. IF stage b. AF stage c. RF stage d. None of these 50. Undesired signal on the other side of the local oscillator output will have the same difference frequency and pass into the IF amplifier. a. Carrier frequency b. Sum frequency c. Difference frequency d. Image frequency

FREQUENCY MODULATION

1. Using Carson’s rule, what is the bandwidth of an FM signal with 5 kHz maximum frequency deviation and 2.5 kHz maximum modulating frequency? a. 14 kHz b. 16 kHz c. 18 kHz d. 15kHz 2. Calculate the maximum bandwidth required of a standard FM broadcast station. a. 156 kHz b. 180 kHz c. 154 kHz d. 160 kHz 3. The operating frequency of an FM transmitter is 168.96 MHz. calculate the frequency of the carrier crystal oscillator if it uses three frequency multipliers – a doubler, a tripler and a quadrupler. a. 7.04 MHz

b. 7.05 MHz c. 7.06 MHz d. 7.07MHz 4. What frequency deviation is caused by noise in an FM receiver which has an input S/N of 2.8 and the modulating frequency of 1.5 kHz? a. 569.2Hz b. 587.3Hz c. 547.8Hz d. 569.2Hz 5. In GM broadcasting, what is the carrier frequency in MHz of a station with a channel number of 285? a. 104.9 MHz b. 104 MHz c. 8 MHz d. 104.5 MHz 6. In FM broadcasting, what is the channel number of the station with a given carrier of 99.1 MHz? a. 254 b. 259 c. 258 d. 256 7. What is the rms output voltage of a PLL FM detector if it uses VCO with proportionality constant of 299 kHz/V and if it receives an FM signal with a deviation of 65 kHz sine-wave modulated? a. 0.25V b. 0.23V

c. 0.24V d. 0.26V 8. A phase-locked loop has a VCO with free-running frequency of 19 MHz. as the frequency of the reference input is gradually raised from zero, the loop locks at 8 MHz and comes out of lock again at 14 MHz. determine the lock range. a. 5 MHz b. 6 MHz c. 8 MHz d. 9 MHz 9. A phase modulator has kp = 2rad/V. what rms voltage of a sine wave would cause a peak phase deviation of 30 degrees? a. 0.184V b. 0.156V c. 0.187V d. 0.185V 10. A system uses a deviation of 100 kHz and a modulating frequency of 15 kHz. What is the approximate bandwidth? a. 235 kHz b. 234 kHz c. 230 kHz d. 236kHz 11. A phase-locked loop has a VCO with a free-running frequency of 14 MHz. as the frequency of the reference input is gradually raised from zero. The loop locks at 12 MHz and comes out of lock again at 18 MHz. calculate the capture range. a. 4 MHz b. 5 MHz c. 6 MHz

d. 7MHz 12. What is the frequency swing of an FM broadcast transmitter when modulated 80%? a. 60 kHz b. 62 kHz c. 63 kHz d. 64kHz 13. Determine the modulation index of a standard FM broadcast having a hypothetical maximum carrier frequency deviation of +- 12 kHz and a maximum modulating frequency of 4 kHz. a. 5 b. 4 c. 3 d. 2 14. What is the modulation index of an FM transmitter whose frequency deviation is 50 kHz, while its audio frequency is 10 kHz? a. 8 b. 6 c. 7 d. 5 15. The carrier swing necessary to provide 80% modulation in the FM broadcasting band is ____? a. 120 kHz b. 130 kHz c. 140 kHz

d. 150 kHz 16. An FM signal has a center frequency of 100 MHz but is swinging between 100.01 MHz and 99.999 MHz at a rate of 100 times per second, what is the modulation index of the signal? a. 110 b. 100 c. 90 d. 80 17. If the frequency fed to the pre-amplifier of a basic transmitter with multipliers is composed of a pair of triples and a doublers multipliers is 198 MHz. what frequency should the oscillator operate? a. 10 MHz b. 11 MHz c. 12 MHz d. 13MHz 18. For commercial FM broadcasting the maximum permissible range in modulation index is 5 – 2500. What is the maximum bandwidth needed for this system? a. 180 kHz b. 190 kHz c. 200 kHz d. 210kHz 19. A portable radio transmitter has to operate at temperatures from – 5 degrees to 35 degrees C. if its signal is derived from a crystal oscillator with a temperature

coefficient of +1 ppm per degree centigrade, and it transmit at exactly 145 MHz at 20 degrees C, find the transmitting frequency at 35 degrees C. a. 145.002175 MHz b. 145.002174 MHz c. 145.002176 MHz d. 145.002154MHz 20. What FM channel is 107.5 MHz carrier? a. 299 b. 298 c. 297 d. 296 21. The instantaneous value of the modulating signal to and FM modulator is -2V, sensitivity kf = 25 kHz/V and operating at a carrier frequency of 88 MHz. determine the output frequency of the modulator. a. 87.59 MHz b. 95.32 MHz c. 87.95 MHz d. 84.65 MHz 22. Calculate the frequency deviation of an Fm modulator that has kf = 20 kHz/V and operates at a carrier frequency of 99.1 MHz modulated by a 2.5 Vrms sine wave. a. 70.5 kHz b. 70.6 kHz

c. 70.7 kHz d. 70.8kHz 23. Find the deviation ratio of an FM broadcast transmitter if the frequency of the modulating signal varies from 30 Hz to 20 kHz. a. 3.75 b. 3.74 c. 3.73 d. 3.72 24. The output signal of a PM demodulator is 0.54 V. what is the sensitivity of the demodulator if the phase deviation is 30o? a. 0.99rad/V b. 0.98rad/V c. 0.97rad/V d. 0.96rad/V 25. A PM transmitter produces a maximum phase shift of r/3 rad for a modulating frequency of 300 Hz. What is the maximum frequency deviation of the system? a. 315 Hz b. 314 Hz c. 316 Hz d. 317Hz 26. An FM communication system has a sensitivity of kf = 3 kHz/V. how much phase deviation does it produces with a sine wave input of 3 V peak at a frequency of 2 kHz?

a. 4.2rad b. 4.5rad c. 4.3rad d. 4.8rad 27. An FM broadcast transmitter rated output power is 5 W. what is the peak voltage developed across a 50 ohms resistive load? a. 22.34V b. 22.35V c. 22.36V d. 22.37V 28. An FM system has a modulation index of 3 and its corresponding Bessel coefficient; Jo = -0.26; J1 = 0.34; J2 = 0.49; J3 = 0.31. Find the RMS carrier voltage if the total power is 5 W. developed across a 50 ohms resistive load. a. 4.16V b. 4.11V c. 4.23V d. 4.56V 29. Suppose the total power of an FM signal is 7W. What is the power of the second sideband if the modulation index is 3? J0 = -0.26; J1 = 0.34; J2 = 0.49; J3 = 0.31. a. 3.4W b. 3.5W c. 3.6W

d. 3.2W 30. An FM broadcast transmitter has a deviation of 25 kHz and a modulating frequency of 8 kHz. Calculate the power that is unaccounted, if the total power PT is 10 W. J0 = -0.26; J1 = 0.34; J2 = 0.49; J3 = 0.31. a. 0.289W b. 0.288W c. 0.283W d. 0.254W 31. A certain FM station transmitted a modulating frequency of 25 kHz and a frequency deviation of 75 kHz. What is the approximate signal-to-noise ratio at the detector output if the signal-to-noise ratio at the input to the receiver detector is 20 dB? a. 34dB b. 35dB c. 36dB d. 37dB 32. An FM broadcast station transmits a 3 kHz test tone, and a frequency deviation of 15 kHz. Determine the modulation index. a. 2 b. 3 c. 5 d. 4

33. An FM signal with modulation index of 4 and modulating frequency of 8 kHz. What is the frequency deviation of the signal? a. 36 kHz b. 35 kHz c. 31 kHz d. 32kHz 34. A certain FM modulator has kf = 25 kHz/V. Suppose the peak amplitude of the modulating signal is 3 V at a frequency of 3 kHz, determine the modulation index of the signal. a. 25 b. 26 c. 27 d. 28 35. The output frequency of the modulator increases by 50 kHz. What is the dc voltage applied to the FM modulator, if the deviation sensitivity is 25 kHz/V? a. 5V b. 4V c. 3V d. 2V 36. The maximum instantaneous frequency of the modulated signal is 95.05 MHz. if a 5 kHz signal modulates a 95 MHz carrier, calculate the modulation index of the signal. a. 10

b. 1 c. 11 d. 12 37. A PM signal has a RMS signal of 3 V at a frequency of 3 kHz. If the modulation index of the signal is 15, determine the sensitivity of the modulator. a. 3.54rad/V b. 3.53rad/V c. 3.55rad/V d. 3.52rad/V 38. The modulation index of the PM signal is 2. If a modulating signal that has amplitude of 50 mV at a frequency of 3 kHz phase modulates a 90 kHz carrier signal, what would be the new modulation index of the signal? Assume that the amplitude of the modulating signal is increased by 50%. a. 5 b. 4 c. 3 d. 2 39. A sine wave of frequency 15 kHz modulates a carrier at 101.1 MHz. the peak frequency deviation is 75 kHz. Determine the peak amplitude of the modulating signal if the sensitivity of the modulator is 50 rad/V. a. 40mV b. 300mV c. 220mV

d. 100mV 40. With a maximum frequency deviation of 75 kHz, what is the maximum phase deviation that can be present in an FM radio broadcast signal, assuming it transmits a baseband frequency of 50 Hz to 20 kHz? a. 1560rad b. 1500rad c. 1540rad d. 1546rad 41. The phase shift of a phase modulated signal is 86 degree. What is the modulation index of the said signal? a. 1.2 b. 1.5 c. 1.3 d. 1.6 42. Determine the modulation index of an FM signal, given that the modulating frequency is 25 kHz and frequency deviation of 75 kHz. a. 3 b. 5 c. 4 d. 6 43. Suppose a certain FM signal uses a frequency deviation of 100 kHz and a modulating index of 5. Calculate the band width using Carsons rule. a. 250kHz

b. 240kHz c. 260kHz d. 230kHz 44. An FM station transmits 100 W of power. If the modulation index of the signal is 7, how much power is transmitted at the carrier frequency if Jo = 0.4? a. 16W b. 17W c. 18W d. 19W 45. A 50 ohms dummy load is used to test a certain FM station. Suppose the measured power is 12.5 W, what is the voltage level of the second sideband if a frequency of 5 kHz test tone is used and a 10 kHz frequency deviation? a. 8.45Vrms b. 8.56Vrms c. 8.75Vrms d. 8.26Vrms 46. An FM receiver can sufficiently receives only the carrier and the first two sets of side bands. If the total power of the signal is 20 W, deviation of 25 kHz, and a modulation index of 10, what is the percentage of the total signal power will it receive? a. 96.62% b. 96.65% c. 96.68%

d. 96.56% 47. An FM receiver sufficiently receives only the carrier and the first two sets of sidebands. If the total power of the signal is 10 W, deviation is 25 kHz, and the modulation index is 10, how much power is transmitted at the carrier frequency? a. 485mW b. 484mW c. 456mW d. 481mW 48. The calculated bandwidth using Carsons rule is 40 kHz if the modulating frequency of the signal is 5 kHz. Using the same signal, what is the bandwidth if sidebands with more than 1% of the signal voltage are considered? a. 61 kHz b. 62 kHz c. 60 kHz d. 63kHz 49. An FM transmitter operates with a carrier power of 10 W. what is the total signal power if the modulation index of the signal is 5? a. 308W b. 309W c. 310W d. 311W 50. The maximum phase deviation given to the signal by the noise voltage is 0.01radian. What is the signal to noise ratio at the detectors input?

a. 41dB b. 42dB c. 43dB d. 40dB 51. An FM receiver detects a 100 mV signal. A spurious signal is also detected by the receiver that resulted to an S/N of 40 dB at the detectors output. Determine the minimum S/N ratio at the detectors output if the modulating frequency is 2 kHz and frequency deviation of 50 kHz. a. 12dB b. 13dB c. 14dB d. 15dB 52. An FM receiver is tuned at 99.1 MHz. what is the IF rejection ratio if the receiver consists of a single tuned circuit with Q of 45? a. 23dB b. 24dB c. 25dB d. 26dB 53. An FM detector receives an FM signal with a deviation of 15 kHz. What is the peak to peak output voltage of the detector if its sensitivity is 75 microV/Hz? a. 2.25V b. 2.26V c. 2.27V

d. 2.28V 54. An FM receiver uses PLL to detect the signal. What is the sensitivity of the VCO in the PLL if the output of the detector is 1.25 Vp from an FM signal that is modulated to 10 kHz deviation by a sine wave? a. 5 kHz/V b. 6 kHz/V c. 7 kHz/V d. 8 kHz/V 55. An FM receiver uses a tuned transformer operating at 10.7 MHz. what is the bandwidth using the optimum coupling factor if the primary circuit has a Q of 50 and the secondary has Q of 35? a. 383.6 kHz b. 383.7 kHz c. 383.8 kHz d. 383.9 kHz 56. An FM super heterodyne receiver is tuned to a frequency of 88 MHz. what is the local oscillator frequency if low side injection is used at the mixer? a. 77.3 MHz b. 77.4 MHz c. 77.5 MHz d. 77.6MHz